Bab el-Mandeb Strait

The southern gate of the Red Sea corridor

Bab el-Mandeb is the narrow entrance at the bottom of the Red Sea. Everything that reaches the Suez Canal from the Indian Ocean passes through here first, which makes it the earlier and sharper of the two readings — traffic turns away at the gate rather than at the canal.

It fell further and faster than Suez did, and the two have moved together since.

Traffic was conserved, not lost

The vessels that stopped appearing here did not stop sailing. The Cape of Good Hope has carried close to double its own baseline over the same period, and the gain there is a similar size to the loss here.

That conservation is why the Route Displacement Index measures how traffic is distributed rather than how much there is. A world total would show almost nothing happened. Rerouting around a continent is not nothing.

Reading the two baselines

Against 2019–2023 this route is down by more than a third. Against the last twelve months it is close to unchanged. Both are accurate and they describe different things: the first is the size of the dislocation, the second is whether it is still moving. Here it is not — the level has been stable for a long time.